1. Field of the Invention
The present invention relates to a light source control apparatus and a light source control method for controlling a plurality of parallel-connected light sources.
2. Background Art
It has recently been suggested that a collection of a plurality of light emitting diodes (LEDs) electrically connected in parallel be used as a light source for a projection image display apparatus. Connecting LEDs in parallel can drive a large number of LEDs at low voltage. Besides, turning on a plurality of LEDs can obtain a high-luminance light source. An apparatus including a light source composed of a plurality of parallel-connected LEDs can therefore reduce the power consumption of the entire apparatus compared with a conventional apparatus including a lamp light source.
An apparatus including a plurality of LEDs needs to control the luminance of each LED. Japanese Patent Application Laid-Open Nos. 2007-095391 (paragraphs 0013 to 0016. FIG. 1) and 2007-096113 (paragraphs 0018 and 0019, FIG. 1) each disclose the technology (hereinafter, also referred to as “related art A”) of controlling a plurality of LEDs.
Unfortunately, with the configuration including a light source unit composed of a plurality of parallel-connected LEDs, all of the LEDs may fail to light up due to any fault occurring in only one of the plurality of LEDs.
For example, if a short-circuit fault occurs in one of a plurality of LEDs constituting a light source unit, the LED having a short-circuit fault is intensively supplied with a drive current from a constant current circuit. Consequently, all the LEDs do not light up.